Electrical speed-responsive system with variable-ratio drive



Dec. 9, 1947. D, w, MOORE, R 2,432,327

ELECTRICAL SPEED-RESPONSIVE SYSTEM WITH VARIABLE-RATIO DRIVE Filed Nov. 17, '1944 .Z0226 Z- 29 590, 19a 1% 10 l9 IN VEN TOR.

Patented Dec. 9, 1947 UNITED STATES. PATENT OFFICE ELECTRICAL SPEED-RESPONSIVE. SYSTEM, WITH VARIABLE-RATIQ DRIVE David W. Moore, Jr., New York, N; Y., assignor toFairohild Camera and Instrument Corporation, a corporation of Delaware ApplicationNovember17, 1944,,S erial No. 563,922

3 Claims. 1

This invention relates to speed-responsivesystems-for-deriving an electrical signal varying with.

obtain such an effect linearly representative of speed; il s-contrasted to many speed-responsive devicesof the prior art-having a square-law or other power.law characteristic and requiring individual calibratingorrectifying arrangements to derive the required linearly-relatedspeed parameter.

It: isan object of the invention, therefore, to provide a new and improved speed-responsive system by means ofwhich there may; be developed anelectricalsignal representative of the speed of a rotating element. 2

Itisanother object of theinvention to provide a new and improvedspeed-responsive system for deriving an electrical signal representative of the speed ofa primary rotating element in which the derived signal is substantially linearly representw tiVQDfgt-hfi speed of the primary rotating element.

Inaccordancewith the invention, a speed-respcnsive system for deriving an electrical signal varying with the speed of a primary rotating element comprises a reference-speed secondary rotating elementand a continuously-variable-ratic drive between the primary and: secondary elements Thisvariable ratio drive includes a driven element having-a driving connection with both of the primary:a-ndsecondary elements and the driven element is movable by one of, the primary and secondary elements to equalize the speed ratios qf lts drivingengagements with the primary and secondary elements. The system also includes ineansactuated by the movement of said driven element for deriving an electricalsignal representative. of the ratio of the speeds of the primary andsecondar ,elements. Preferably the second- I ary element is av constant-speed rotating element and-the derivedelectrical signal is linearly rep-,

resentativeof the speed of theprimary element.

For a better understanding of the invention, together with other and further objects thereof, reference .is :had to the following. description taken in connectionwith thev accompanying drawings while itsscope will bepointed-out in the appended 3 3 1.51

Beferringnow -to tiredmwings, Fig. l is a sideele tiq fi i n a r ssnonsiv svstememb vi a 2 the invention; Fig. 2-is a top plan view of'the apparatus of Fig.- 1 with the top cover plate removed; while Fig. 3 is a fragmentary view of a modified form of continuous variable-ratio drive which may be utilized in the system of Figs. 1 and 2.

Referring now to Figs, 1 and 2 of the drawings,

there is illustrated'a speed-responsive system for deriving an electrical signal variable with, preferably linearly representative of, the speed of a primary rotating element or shaft l9. This systern includes a reference-speed secondar rotating element or'shaft' I I which may be driven by a suitable motor 12 through a gearing l3; Preferably the motor i2 is a constant-speedmotor and drives the secondary shaft H at constant. speed. The shaft H! is journalled in bearings Li, M of; a frame l5, while the shaft ii is journalled in a bearing H5- in an extension [5a of the frame l5 and in a bearing (not shown) in the base plate [5b of frame I5, the axes of the shafts H1 and H lying in the same plane and being normal to each other.

The system includesalso a continuous variableratio drive between the primary shaft H] and the secondary shaft 5 This variable-ratio drive may take an of several forms, but in a preferred embodiment it consists of a variable-radius driving element such as a friction disc ll attached to and driven by the secondary shaft H, the as sembly being supported vertically on an antifriction thrust bearing It resiliently supported by a spring Id. The variable-ratio drive also includes a constant-radius driven element having a driving engagement with both the driving element I! and the primary shaft Iii. For example, the driven element may comp rise a traveling nut; 20 having a constant-radiusfriction rollerilla engaging thefriction surface of the disc I! and a translatory driving engagement with the primary shaft H), as b being internally threaded and engaging a threaded portion ifla of the shaft IEI. Due to the normal relation between the axes of the shafts l8 and H, thedriving surface of the variable-radius device'or-disc l'l' issubstantially parallel to the axisof rotation ofthe" with the speed of the primary shaft as, there is mounted in the frame l5 parallel to the shaft 10 aguide bar 2| on which is mounted a sliding sleeve- 22 having an extending arm 22a terminating in a bifurcated yoke 22b engaging an annular recess 2% in the nut 20. By this arrangement, the sleeve 22 is moved transversely in accordance with the movement of the traveling nut 20 on the shaft I0. There is mounted on the sleeve 22 an adjustable sliding contact 25 bearing on an elongated voltage divider resistor 25 supported on the frame l5 parallel to the axis of sleeve 22. The terminals of the voltage divider resistor 26 are connected to suitable supply circuit terminals 21, while electrical signal-output terminals 28 are connected to the adjustable contact 25 and to the terminal 21 connected to the end of the resistor 25 contacted by the element 25 when in the zero position of the system. If desired, a visual indication varying with the speed of the primary shaft Ill may be obtained by attaching to the sleeve 22 a pointer or indicator 23 cooperating with a scale 24 formed on or attached to a member 150 of the frame 15. Also, if desired, a power displacement varying with the speed of the primary shaft l may be obtained by means of a push-rod 22b extending from the sleeve 22 and through the frame i and effective to actuate any mechanically controllable device.

In applications involving unidirectional operation of primary shaft l0, threaded portion Illa need not be extended to carry the nut 20 beyond its zero position in which the roller 20a contacts the center of the disc l1, and there may be provided a sleeve 29 mounted on the shaft l0 and secured thereto by a key 29a and serving as a stop, preventing the movement of the nut 20 beyond its zero position.

It is believed that the operation of the system illustrated will be apparent from the foregoing description. In brief, however, assuming that the secondary shaft H and the friction disc I! are rotating and that the primary shaft I0 is stationary, the parts are in the relative positions shown in Figs. 1 and 2. If now the shaft I0 is rotated, the traveling nut 20 will be engaged by the threaded portion Illa of the shaft and will be moved axially of the primary shaft 10 by its translatory or threaded engagement therewith to equalize the speed ratios of its driving engagements with the primary shaft 10 and the secondary shaft II, that is, until the roller 20a has the same peripheral speeds with respect to the axes of rotation of both of the shafts l9 and II. At this point, the speed of rotation of the nut 20, as driven by the disc IT, corresponds to the speed of rotation of the shaft l0 and there will be no further axial or translatory movement of the nut 20. Axial movement of the driven element or nut 20 along the shaft [0 actuates the sleeve 22 and the adjustable contact 25 of voltage divider 26 to develop at the terminals 28 an electrical signal or a resistance value representative of the ratio of the speeds of the primary shaft Ill and secondary shaft ii. If the voltage-divider 26 has a linear displacement-resistance characteristic, the electrical signal developed at the output terniinals 28 will be linearly representative of the ratio of the speeds of the shafts l0 and l I. Similarly the signal output at terminals 28 may be made to represent any desired function of the ratio of the speeds of the shafts l0 and H by properly shaping the displacement resistance characteristic of voltage divider 26. At the same time, axial movement of the sleeve 22 moves the pointer 23 along the scale 24, the movement of these elements giving a visual indication repre sentative of the ratio of the speeds of the primary shaft l0 and the secondary shaft ll. Also, the axial movement of sleeve 22 results in movement of the push-rod 22b to actuate any suitable mechanically controllable device.

In the preferred embodiment of the speedresponsive system illustrated and described, the motor [2 and secondary shaft ll rotate at constant speed and the output effects, that is, the electrical signal, the visual indication and the power displacement, are linearly representative of the speed of the primary shaft [0. However, by a proper tapering or shaping of the displacement-resistance characteristic of the resistor 26, the output electrical signal or resistance value may be made to follow any predetermined function of the speed of the primary shaft In. However, if the motor l2 and secondary shaft ll rotate at a variable speed, the output electrical signal is representative of the ratio of the speed of the shaft 10 to that of the shaft H. In this latter case, either shaft may be considered as the primary shaft and the other, the secondary shaft.

In the apparatus illustrated in Figs. 1 and 2, when the primary shaft I0 is not rotating and the roller 28a is at the center of the disc I1, there is a slight wear on the roller 20a due to the rotation of the disc IT. This may be avoided by the modifled construction shown schematically in Fig. 3 in which the single roller 26a is replaced by a pair of rollers 30a and 30b actuating the crown gears 3m, 31b of a differential mechanism. The ring gear 3lc of the differential, attached to the housing 3ld, drives the traveling nut 32 through a gear 33, the nut 32 engaging the threaded portion Illa of shaft [0, in a manner similar to the structure of Fig. 1, and driving the indicating pointer 23 and adjustable contact 25 in a similar manner, by mechanism not shown.

In the operation of the apparatus of Fig. 3 the rollers 30a and 301) are disposed to rotate on opposite sides of the center of the disc I! and the design constants of the apparatus are so selected that, for the range of speed of the primary shaft l to be measured, neither of the rollers 30a and 38b moves beyond the center of the disc l'l. With this arrangement the rollers 30a and 30b always rotate, but in opposite directions. The ring gear 320 is driven at a speed which is the average of the speeds of the rollers 30a and 30b and corresponds to the speed of the disc I! at a point immediately beneath the center point of the differen tial gear 3la, 31b, (lie. The traveling nut 32 is driven, therefore, in a manner exactly similar to the structure of Figs. 1 and 2 and the visual indication and developed output electrical signal are in all respects similar to those obtained by the structure of Figs. 1 and 2.

While the variable-radius driving element of the invention has been illustrated as a friction disc, it will be apparent that there may be substituted therefor a tapered pulley or drum or other equivalent variable-radius driving element.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed as new is:

1. A speed-responsive system for deriving an electrical signal varying with the speed of a primary rotating element comprising, a referencespeed secondary rotating element, a continuously variable-ratio drive between said primary and secondary elements including a driven element having a driving connection with both said primary and secondary elements, said driven element being movable by one of said primary and secondary elements to equalize the speed ratios of its driving engagements With said primary and secondary elements, and means actuated by the movement of said driven element for developing an electrical signal representative of the ratio of the speeds of said primary and secondary elements.

2. A speed-responsive system for deriving an electrical signal representative of the speed of a primary rotating element comprising, a constantspeed secondary rotating element, a continuously variable-ratio drive between said'primary and secondary elements including a driven element having a driving connection with both said primary and secondary elements, said driven element being movable by one of said primary and secondary elements to equalize the speed ratios of its driving engagements with said primary and secondary elements, and a voltage divider having an adjustable contact actuated by the movement of said driven element for developing an electrical signal representative of the speed of said primary element.

3. A speed-responsive system for deriving an electrical signal representative of the speed of a primary rotating element comprising, a constantspeed secondary rotating element, a continuously variable-ratio drive between said primary and secondary elements including a driven element having a driving connection with both said primary and secondary elements, said driven element being movable axially by one of said primary and secondary elements to equalize the speed ratios of its driving engagements with said primary and secondary elements, an elongated resistor disposed parallel to the axis of said driven element, and an adjustable contact actuated by said driven element and cooperating with said resistor to provide a resistance value representative of the speed of said primary element.

DAVID W. MOORE, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

